CSLB C-10 Electrical ContractorSafety and TestingMedium
A technician is preparing to work on a 480V motor control center. Which of the following is the LAST step to verify the absence of voltage AFTER applying lockout/tagout devices?
- ANotify all affected personnel that the equipment is de-energized.
- BUse a properly rated voltage tester to confirm zero voltage on all phases and ground.
- CAttempt to start the equipment to confirm it does not energize.
- DVisually inspect all lockout/tagout devices for proper placement.
Show answer & explanationAnswer & explanation
Correct answer: B. Use a properly rated voltage tester to confirm zero voltage on all phases and ground.
After applying lockout/tagout devices, the final and most critical step before starting work is to verify the absence of voltage using a properly rated and tested voltage detector. This ensures the circuit is truly de-energized and safe to work on.
Why the other options are wrong
- A. Notifying personnel occurs after lockout/tagout and testing, but before starting work; the question asks about verifying absence of voltage AFTER LOTO.
- C. Attempting to start the equipment is an early step in the LOTO procedure, before verifying zero voltage.
- D. Visual inspection of LOTO devices is an important step, but it precedes the actual verification of zero voltage.
Absence of Voltage Verification
The final confirmation using a test instrument that an electrical circuit or equipment is de-energized after lockout/tagout procedures have been applied.
- Must use a properly rated and tested voltage detector.
- Check all phases, conductors, and ground points.
- Performed immediately before beginning work on the equipment.
Memory trick: Always Start The Process, Isolate, Lock, Test, Then Work Safely.